Methods for forming and protecting electrical interconnects and resultant assemblies

ABSTRACT

The described embodiments relate to methods and systems for forming and protecting electrical interconnect assemblies. In one embodiment, an electrical interconnect assembly forming method forms an electrical interconnect between one or more conductors of a first support structure and one or more conductors of a second support structure. The method also distributes a generally flowable material over the electrical interconnect and exposes the generally flowable material to conditions sufficient to render the generally flowable material into a generally non-flowable state that provides fluid protection to the electrical interconnect and supports the electrical interconnect to reduce stress concentration at the electrical interconnect.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 10/426,584, filed Apr. 30, 2003 now U.S. Pat. No. 6,913,343, which is hereby incorporated by reference.

BACKGROUND

Electronic devices which operate in potentially deleterious environments pose challenging design problems. The environment may be due to external factors or to conditions caused by the electronic device itself. In one such example, ink jet printing devices eject fluidic ink from multiple nozzles arranged on one or more print cartridges onto a print media to form a desired image. During the ink ejection process, some of the ink that is ejected does not actually contribute to the desired image, but instead becomes what is generally referred to as “non-target ink”.

This non-target ink can assume various forms. Generally, the non-target ink becomes an aerosol, a powder, or liquid colloid among others, and as such can drift and land on components of the printing device especially the print cartridge(s). The non-target ink can degrade certain components, most notably various electrical conductors that are commonly comprised of metal. The conductors can be especially difficult to protect from degradation where two or more conductors form a connection or “electrical interconnect”.

For these and other reasons, there is a need for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The same components are used throughout the drawings to reference like features and components.

FIG. 1 shows a front elevational view of an exemplary printing device.

FIG. 2 shows a perspective view of an exemplary print cartridge according to an embodiment of the present invention suitable for use in some exemplary printing devices.

FIG. 3 shows a perspective view of another exemplary print cartridge according to an embodiment of the present invention suitable for use in some exemplary printing devices.

FIG. 4 shows a cross-sectional view of the exemplary print cartridge as shown and indicated in FIG. 3.

FIG. 5 shows a cross-sectional view of an enlarged portion of the cross-section shown in FIG. 4.

FIG. 6 shows a cross-sectional view of components that can be configured to form an exemplary electrical interconnect assembly in accordance with one embodiment.

FIG. 7 shows a cross-sectional view of components that can be configured to form an exemplary electrical interconnect assembly in accordance with one implementation of one embodiment.

FIG. 8 shows another cross-sectional view of components that can be configured to form an exemplary electrical interconnect assembly in accordance with one implementation of one embodiment. In this representation, the components are positioned in a workstation

FIG. 9 shows a cross-sectional view of an exemplary electrical interconnect assembly positioned in a workstation in accordance with one embodiment.

FIG. 10 shows a cross-sectional view of an exemplary electrical interconnect assembly in accordance with one embodiment.

FIG. 11 shows a cross-sectional view of another exemplary electrical interconnect assembly in accordance with one embodiment.

FIG. 12 shows a cross-sectional view of another exemplary electrical interconnect assembly in accordance with one embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OVERVIEW

The embodiments described below pertain to methods for protecting electrical interconnects from degradation. An electrical interconnect comprises at least one conductor electrically coupled or interconnected to another conductor. One suitable electrical interconnect comprises a first conductor that is electrically coupled to a second conductor with solder or other material. The electrical interconnect has a protective material positioned over at least a portion thereof to protect the electrical interconnect from degradation. In some embodiments, the protective material is distributed in a generally flowable state around at least a portion of the electrical interconnect and/or proximate portions of the first and second conductors. The protective material can then be rendered into a generally non-flowable state that can provide fluid and/or ink protection to the electrical interconnect.

The electrical interconnects commonly occur as “electrical interconnect assemblies” where one or more conductors are supported by a first support structure and are electrically interconnected to one or more conductors supported by a second support structure. The electrical interconnect can be especially susceptible to degradation and can be protected by the protective material. In some embodiments, the protective material can also provide electrical insulation and/or mechanical stabilization to the electrical interconnect assembly.

The embodiments described herein are employed in the context of electrical interconnect assemblies that comprise a portion of an ink jet print cartridge. It is to be appreciated and understood that various embodiments are equally applicable in other non-ink jet contexts as well. For example, a coastal marine environment can expose electrical devices to moist, salt laden air which can promote degradation of the device. The described embodiments can be utilized to reduce such degradation.

Exemplary Printing Device

FIG. 1 shows a printing device, embodied in the form of an ink jet printer 10. The printer 10 may be capable of printing in black-and-white and/or in color. The term “printing device” refers to any type of device which ejects fluids, such as dye or pigment based inks, or other suitable materials onto a print media to form a desired image. Though an inkjet printer is shown for exemplary purposes, it is noted that aspects of the described embodiments can be implemented in other forms of printing devices that employ inkjet printing elements or other fluid ejecting devices, such as facsimile machines, photocopiers, and the like.

FIG. 2 shows a print cartridge 20 that can be installed in the ink jet printer 10. The print cartridge can be electrically coupled with and controlled by a controller, such as a processor, to selectively eject ink to form a desired image.

The print cartridge 20 has one or more print head(s) 22 each of which includes one or more nozzle(s) 24 arranged in one or more generally linear nozzle array(s) 26. A fluid, such as ink, can be selectively ejected from individual nozzles 22 to create a desired image on a print media such as paper, transparencies, etc. In various embodiments, the print cartridge 20 and/or the print media can be moved relative to one another to form portions of the desired image. The print cartridge 20 can contain an internal ink source and/or be connected to an external ink source for supplying ink to the various nozzles 24.

FIG. 2 shows a print cartridge 20 that can be installed in printing devices, such as ink jet printer 10. The print cartridge can be electrically coupled with and controlled by a controller, such as a processor, to selectively eject ink to form a desired image on a print media. A print cartridge may be designed to be replaceable during the life of the printing device or may be designed to have a functional lifespan equal to or greater than the printing device.

FIG. 3 shows a print cartridge 20 a that has multiple print heads 22 a, individual ones of which comprise two generally linear nozzle arrays 26 a. Each array has multiple nozzles 24 a. The print heads 22 a are positioned on a first support structure 30 of the print cartridge 20 a. In this example, the first support structure 30 is oriented generally orthogonally to a second support structure 32. Collectively, first and second support structures provide an electrical interconnect assembly 34 which will be described in more detail below.

EXEMPLARY EMBODIMENTS AND METHODS

FIG. 4 shows a cross-sectional view taken transverse a long axis of print cartridge 20 a as indicated in FIG. 3. As shown in FIG. 4, first support structure 30 supports print heads 22 a and a first conductor 40. Second support structure 32 supports a second conductor 42. Support structures 30, 32 can support one or more conductors in various configurations including, but not limited to, portions and/or an entirety of the conductor being positioned on or within the support structure among others.

In this embodiment, the first conductor 40 is electrically coupled to print head 22 a. The first conductor is also electrically coupled to the second conductor 42 at electrical interconnect 44 which is described in more detail below.

The first and second support structures 30, 32 can be comprised of any suitable material or materials. Additionally, the first support structure 30 can comprise the same materials as the second support structure or the support structures can comprise different materials. For example, in one embodiment, the first support structure is comprised of ceramic, such as a multilayer ceramic, while the second support structure comprises a polymer. Suitable support structures can be formed from a single material, or from multiple materials. Such support structures can be formed in any suitable way, such as injection molding, or formation of a composite material.

FIG. 5 shows an enlarged portion of print cartridge 20 a shown in FIG. 4. FIG. 5 shows electrical interconnect assembly 34 comprising first support structure 30 and associated first conductor 40 along with second support structure 32 and associated second conductor 42. Electrical interconnect 34 also includes electrical interconnect 44, and a protective material 52 positioned over the electrical interconnect 44.

Electrical interconnect 44 electrically couples the first conductor 40 and the second conductor 42. Protective material 52 essentially surrounds the electrical interconnect 44 sufficiently to provide ink protection for the electrical interconnect. The protective material 52 can comprise any suitable material. One type of protective material comprises epoxy. The skilled artisan will recognize other suitable protective materials.

In some embodiments, an electrically conductive material, which in this embodiment comprises solder 54 electrically couples first and second conductors 40, 42 at electrical interconnect 44. As such, in this embodiment, electrical interconnect 44 comprises solder 54 and a portion of each of conductors 40, 42.

Alternatively or additionally to solder, other suitable electrically conductive materials can comprise, but are not limited to, conductive adhesives and braze materials. The discussion below refers to solder, but it is to be understood that other such electrically conductive materials can also be utilized.

In some embodiments, protective material 52 can also bond with, or otherwise adhere to, the first and/or second support structures 30, 32, and/or portions of the associated conductors at the electrical interconnects, to provide further ink protection. Further, in some of the embodiments other benefits associated with the protective material may also be realized.

For example, in some embodiments the protective material can provide increased mechanical strength between the first and second support structures. Alternatively or additionally, the protective material may also provide increased stabilization of the electrical interconnects. Some illustrative examples will be discussed in more detail below.

FIGS. 6-9 show a process for forming an electrical interconnect assembly.

Referring to FIG. 6, first support structure 30 a supports a first set of conductors 40 a, 40 b. In this example, individual conductors 40 a and 40 b can have a terminal portion comprising terminal pads 60 a and 60 b respectively.

Conductors 40 a, 40 b can have solder 54 a positioned thereon. In this embodiment, individual solder portions are positioned respectively on each of the individual terminal pads 60 a, 60 b. In some embodiments, the solder 54 a comprises solder paste which can be silk-screened in a desired pattern to precisely position solder paste onto the individual conductors 40 a, 40 b and/or their respective terminal pads 60 a, 60 b as shown here. In some other embodiments, the solder paste can be stencil printed or hot-air leveled, among other methods of positioning. In some embodiments, solder 54 a can have a cleaning component, such as a flux, to facilitate formation of an effective electrical interconnect as described in relation to FIG. 7.

FIG. 6 further shows a second support structure 32 a supporting a second set of conductors comprising conductors 42 a and 42 b. Individual conductors 42 a and 42 b can have a terminal portion 62 a and 62 b respectively, that is oriented generally non-parallel to a majority of the associated conductor. In this embodiment, the terminal portions 62 a and 62 b comprise what is known as a “j-leg” configuration. The j-leg conductor configuration is characterized by an elongate, generally straight conductor portion that extends along a long axis toward a terminal portion that is not generally straight, but rather curved. The generally straight conductor portion constitutes a majority of the conductor, and the terminal portion extends generally away therefrom.

To achieve a desired electrical interconnect assembly, terminal portions of conductors supported by a given support structure may be arranged in various configurations. For example, the terminal portions may be arranged in linear or staggered configurations, among others.

FIG. 7 shows the terminal portions 62 a, 62 b of conductors 42 a, 42 b positioned in electrical contact with the solder 54 a and terminal pads 60 a and 60 b of the first support structure. The solder 54 a can be melted and subsequently allowed to harden to form an effective electrical interconnect 44 a.

In some embodiments, suitable solder can be chosen based on factors such as the melting temperature of the solder relative to a temperature at which damage may occur to the various components, such as first support structure 30 a and second support structure 30 b. Solder can be melted in any suitable way including, but not limited to, placing the components in a heated environment (oven) or positioning a thermal component in proximity to the solder to cause the solder to melt.

In this embodiment, the first and second support structures 30 a, 32 a are oriented generally perpendicular to one another. This can be seen by comparing the orientation of the first support structure's long axis designated x to the orientation of the second support structure's long axis designated y. Other embodiments can position the support structures generally parallel to one another or at other various angles relative to the two associated long axes. Several such examples are provided below in relation to FIGS. 10-12.

In some embodiments, a desired relative orientation of the first and second support structures can be achieved by holding the support structures at a desired angle while causing the protective material to become generally non-flowing. In some embodiments, the desired orientation can be different than the orientation during formation of the electrical interconnect.

In some embodiments, the electrical interconnect can also be annealed. Annealing can in some instances reduce stress in an electrical interconnect assembly. Annealing can occur at any suitable sequence in the formation of an electrical interconnect assembly. For example, some embodiments may be annealed after the formation of the electrical interconnect and before the protective material is applied. In some embodiments where heat is used to cure an epoxy protective material, annealing may result indirectly from the curing process. The skilled artisan will recognize other suitable embodiments.

FIGS. 8 and 9 illustrate one suitable implementation for distributing a generally flowable material over the electrical interconnect 44 a. Here, the electrical interconnect assembly 34 a is positioned in a work station 82 such as a jig. The work station 82 orients electrical interconnect assembly 34 a to allow the protective material to be flowed over the electrical interconnect.

FIG. 8 shows the protective material 52 a being distributed with a syringe 84 proximate electrical interconnect 44 a. This is but one suitable distribution technique. Other suitable distribution techniques will be recognized by the skilled artisan.

In some embodiments, protective material 52 a can be selected to have a sufficient viscosity to allow it to flow around the exposed conductors of the electrical interconnect 44 a. In some of these embodiments, protective material 52 a can move or flow, at least in part, due to capillary action. For example, in this embodiment, the distance d (shown FIG. 9) between the first support structure 30 a and the second support structure 32 a can be about 0.008 to 0.010 inches. At such a distance, the generally fluid protective material 52 a can flow between the two support structures, at least in part, due to capillary action. This distance between the first and second support structures is but one exemplary distance where capillary action can contribute to movement of the generally flowable protective material. In some of these embodiments, such capillary action can aid in a more thorough distribution of the protective material 52 a around the electrical interconnect 44 a. In some embodiments, the temperature of the protective material and/or the temperature of the components can be controlled to favorably affect the flow characteristics of the protective material.

FIG. 9 shows the generally flowable protective material 52 a distributed around electrical interconnect 44 a to form a completed electrical interconnect assembly 34 a. In this embodiment, protective material 52 a also contacts first and second support structures 30 a, 32 a, though such need not be the case.

After protective material 52 a is flowed over the interconnect, it can be exposed to conditions sufficient to render it into a generally non-flowable state that provides ink protection for the electrical interconnect. In embodiments, where the protective material 52 a comprises epoxy, such a process can entail curing the protective material. Examples of conditions sufficient to facilitate the protective material becoming generally non-flowing can include heating the protective material, exposing it to UV light, and/or simply allowing it to sit undisturbed for a period of time.

If the material that was flowed over the interconnect is to be heated to harden it, then the appropriate choice for the flowable material is one that does not need to be heated above the melting temperature of the solder in order for it to be hardened. In one such example, a solder can be utilized having a melting temperature of about 200-230 degrees Celsius (C.). An epoxy type protective material can be selected which can be cured by heating it to approximately 120-150 degrees C. for a period of about 20 minutes to about 60 minutes. The skilled artisan will recognize other suitable combinations.

In some embodiments, heating the electrical interconnect assembly to cure the protective material can decrease the stress forces experienced by the various components of the electrical interconnect assembly. For example, where the electrical interconnect assembly is first heated to approximately 230 degrees C. to melt the solder the various components are subject to a large change in temperature upon returning to room temperature. When dissimilar materials are utilized in first and second support structures 30 a, 32 a the different materials may have different coefficients of thermal expansion and thus may be subjected to stress caused by the large change in temperature. Subsequently, if a protective material is applied and the electrical interconnect assembly is heated to a second lower temperature such as 130 degrees C. to cure the protective material, the change in temperature experienced by the electrical interconnect assembly is substantially lessened.

Further, in some embodiments, where the protective material bonds to the electrical interconnect and support structures, stress forces caused by the differing coefficients of thermal expansion may be spread out over a greater region of the electrical interconnect resulting in a lower failure rate of the electrical interconnect assemblies.

FIG. 10 shows a cross-sectional view of another exemplary electrical interconnect assembly 34 c. This embodiment comprises a first support structure 30 c supporting a first conductor 40 c, and a second support structure supporting 32 c supporting a second conductor 42 c. In this embodiment, the two supporting structures 30 c, 32 c and a majority of their associated conductors 40 c, 42 c are oriented at an angle δ that is greater than 0 degrees and is less than 180 degrees. In this particular embodiment, an obtuse angle δ of about 120 degrees is utilized. Other examples may form an acute angle δ. Such an embodiment is described below in relation to FIG. 12. Examples of other suitable configurations are described above and below.

In some embodiments, first conductor 40 c has a terminal portion 60 c comprising a receptacle for receiving a terminal end 62 c of the second conductor 42 c. Inserting the second conductor's terminal end 62 c into the receptacle can form an electrical interconnect 44 c between the two components. This electrical interconnect 44 c may or may not have an electrically connecting material, such as solder, applied thereon either prior to, or subsequent to, inserting the second conductor's terminal end into the first terminal portion's receptacle.

FIG. 11 shows a cross-sectional view of yet another exemplary electrical interconnect assembly 34 d. This embodiment comprises a first support structure 30 d supporting a first conductor 40 d, and a second support structure supporting 32 d supporting a second conductor 42 d. First conductor 40 d has a surface mount portion 60 d comprising a solder ball forming an electrical interconnect 44 d between second conductor 42 d and the surface mount portion.

A protective material 52 d can be distributed around electrical interconnect 44 d to protect the electrical interconnect from degradation. Examples of such degradation are described above and include damage caused by various fluids such as inks. Some inks are water based and contain compounds which can lead to degradation even when the water has evaporated or otherwise dissipated. In such embodiments, a protective material can be selected which protects the electrical interconnect from degradation from fluids and/or various solid compounds which may otherwise damage the electrical interconnect. The skilled artisan will recognize other suitable embodiments.

In the embodiments illustrated above, the first and second support structures 30, 32 are represented as being generally rectangular with two pairs of generally opposing surfaces. Other suitable embodiments can have other suitable configurations.

FIG. 12 illustrates another exemplary electrical interface assembly 34 e. In this embodiment a first support structure 30 e has a first surface 122 that is not parallel to a second surface 124. This configuration can allow second support structure 32 e and a majority of its associated second conductor 42 e to be oriented substantially normally to first surface 122 while the two support structures 30 e, 32 e are non-orthogonal to one another. Such a configuration can, in some embodiments, contribute to ease of assembly and disassembly of an electrical interconnect assembly with other components to form a print cartridge or other functional unit.

In the present embodiment, protective material 52 e provides fluid protection to electrical interconnect 44 e by bonding to first and second support structures 30 e, 32 e. Protective material 52 e can further ensure the integrity of the electrical connections by among other ways stabilizing the electrical interconnect 44 e and associated portions of first and second conductors. This configuration can reduce stress concentrations at the electrical interconnect(s) and distribute such stresses to other portions of the conductors and/or the support structures.

For ease of illustration, many of the exemplary embodiments described above are illustrate only in cross-sectional views. The skilled artisan will recognize that the embodiments are suitable for various arrangements of the conductors on the associated support structures. For example, the described embodiments are applicable to linear or generally linear arrays of electrical interconnects. Further, the described embodiments lend themselves to non-symmetrical configurations of the support structures and associated conductors.

Conclusion

The described embodiments provide methods of assembling electrical interconnect assemblies and resultant assemblies. The electrical interconnect assemblies can allow conductors from two different components or support structures to be electrically connected at an electrical interconnect. The electrical interconnect assembly(s) can have a protective material positioned around the electrical interconnect to reduce degradation caused by ink and/or other materials to the electrical interconnect and associated conductors. The protective material can also provide other advantages such as mechanical stabilization to the electrical interconnect assemblies.

Although the invention has been described in language specific to structural features and methodological steps, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific features or steps described. Rather, the specific features and steps are disclosed as preferred forms of implementing the claimed invention. 

1. An ink jet printer electrical interconnect assembly comprising: a first support structure that surrounds a majority of a first conductor positioned therein, wherein the first conductor has a terminal portion that extends from the first support structure; a second support structure that surrounds a majority of a second conductor positioned therein, wherein the second conductor has a terminal portion comprising a terminal pad that is electrically coupled with the first conductor; and, a protective material covering the terminal portions of the first and second conductors such that no portion of the conductors is exposed adjacent a region in which the first conductor couples with the second conductor and extending between the first and second support structures, wherein the protective material provides ink protection to the first and second conductors and wherein the protective material mechanically stabilizes the first support structure relative to the second support structure.
 2. The ink jet printer electrical interconnect assembly of claim 1, wherein a majority of the first conductor is oriented at angle that is greater than 90 degrees and less than 180 degrees relative to the second conductor.
 3. The ink jet printer electrical interconnect assembly of claim 1, wherein the protective material comprises epoxy.
 4. The ink jet printer electrical interconnect assembly of claim 1, wherein the protective material comprises epoxy which adheres to the terminal portions of the first and second conductors and the first and second support structures.
 5. The ink jet printer electrical interconnect assembly of claim 1, wherein the first support structure comprises multiple first conductors and the second support structure comprises multiple second conductors.
 6. The ink jet printer electrical interconnect assembly of claim 1, wherein the first support structure is oriented at an angle greater than 0 degrees and less than 90 degrees relative to the second support structure when viewed transverse to a long axis of the electrical interconnect assembly.
 7. The ink jet printer electrical interconnect assembly of claim 1, wherein the first support structure and the second support structure have different coefficients of thermal expansion.
 8. The ink jet printer electrical interconnect assembly of claim 1, wherein the first support structure and the second support structure are comprised of different materials.
 9. The ink jet printer electrical interconnect assembly of claim 1, wherein the terminal portions of at least some portion of the first conductor comprises a j-leg.
 10. An electrical interconnect assembly comprising: a first support structure that surrounds a majority of a first conductor; a second support structure that surrounds a majority of a second conductor; an electrical interconnect between a terminal portion of the first conductor not surrounded by the first support structure and a terminal portion of the second conductor not surrounded by the second support structure; and, a protective material essentially surrounding the electrical interconnect such that no portion of the conductors is exposed adjacent a region in which the first conductor couples with the second conductor to provide fluid protection to the electrical interconnect.
 11. The electrical interconnect assembly of claim 10, wherein the terminal portion of the first conductor is oriented generally non-parallel to a majority of the first conductor.
 12. The electrical interconnect assembly of claim 11, wherein the the terminal portion of the first conductor comprises a j-leg.
 13. The electrical interconnect assembly of claim 10, wherein the protective material comprises epoxy.
 14. The electrical interconnect assembly of claim 10, wherein the protective material is bonded to the electrical interconnect.
 15. The electrical interconnect assembly of claim 10, wherein the protective material is bonded to the electrical interconnect and to the terminal portions of the conductors and stabilizes the electrical interconnect by spreading stress forces from the electrical interconnect out to the terminal portions of the conductors.
 16. The electrical interconnect assembly of claim 10, wherein the first support structure and the second support structure are comprised of the same material.
 17. The electrical interconnect assembly of claim 10, wherein the first support structure and the second support structure are comprised of different materials.
 18. The electrical interconnect assembly of claim 10, wherein the first support structure and the second support structure have different coefficients of thermal expansion.
 19. The electrical interconnect assembly of claim 10, wherein the first support structure comprises a polymer.
 20. The electrical interconnect assembly of claim 10, wherein the second support structure comprises a ceramic.
 21. The electrical interconnect assembly of claim 10, wherein the second support structure comprises a multi layer ceramic.
 22. The electrical interconnect assembly of claim 10, wherein the first support structure comprises a polymer and the second support structure comprises a ceramic.
 23. The electrical interconnect assembly of claim 10, wherein the first conductor comprises an elongate conductive structure which extends along a long axis toward its terminal portion, a majority of the long axis of the conductive structure away from the terminal portion being generally straight, the long axis within the terminal portion extending generally away from the long axis majority.
 24. The electrical interconnect assembly of claim 10, wherein the protective material is bonded to the first and second support structures and aids in maintaining an orientation of the first support structure relative to the second support structure.
 25. The electrical interconnect assembly of claim 24, wherein the orientation of the first support structure relative to the second support structure forms an acute angle.
 26. An ink jet print cartridge incorporating the electrical interconnect assembly of claim
 10. 27. An electrical interconnect assembly comprising: means for connecting an electrical interconnect between a conductor of a first support structure and a conductor of a second support structure, wherein the support structures surround their respective conductors adjacent an interconnect area except for terminal portions of the conductors that couple to each other; and, means for protecting the electrical interconnect from degradation that encapsulates the conductor terminal portions to protect them from ink and bonds to the first and second support structures to maintain a desired orientation of the first support structure relative to the second support structure.
 28. The electrical interconnect assembly of claim 27, wherein said means for forming comprises solder.
 29. The electrical interconnect assembly of claim 27, wherein said means for protecting comprises epoxy. 